High efficiency white LEDs with single-crystal ZnO current spreading layers deposited by aqueous solution epitaxy

Abstract

Heteroepitaxial ZnO transparent current spreading layers with low sheet resistances were deposited on GaN-based light emitting diodes using aqueous solution phase epitaxy at temperatures below 90°C. The performance of the LEDs was analyzed and compared to identical devices using electron-beam evaporated indium tin oxide transparent current spreading layers. White LEDs with ZnO layers provided high luminous efficacy–157 lm/W at 0.5A/cm2, and 84.8 lm/W at 35A/cm2, 24% and 50% higher, respectively, than devices with ITO layers. The improvement appears to be due to the enhanced current spreading and low optical absorption provided by the ZnO.

Tunneling-based carrier regeneration in cascaded GaN light emitting diodes to overcome efficiency droop

“…18 The differential series resistance (R s ) of the reported LED was $0.02 X Â cm 2 . 18 We fit the experimental data to the diode equation…”

“…To estimate the efficiency of cascaded LED structures, we combine our estimates of tunneling resistance with the experimental data from the commercial LED published elsewhere so that nonidealities of the active region are taken into account. 18 The modeled reference LED emits at 470 nm and consists of a 1.02 mm 2 mesa area with ZnO layer as contact to p-GaN. 18 The differential series resistance (R s ) of the reported LED was $0.02 X Â cm 2 .…”

“…18 The modeled reference LED emits at 470 nm and consists of a 1.02 mm 2 mesa area with ZnO layer as contact to p-GaN. 18 The differential series resistance (R s ) of the reported LED was $0.02 X Â cm 2 . 18 We fit the experimental data to the diode equation…”

Synthesis of ZnO Nanowire Array Film on Mg-Doped Gallium Nitride Substrate by Simple Hydrothermal Method

“…ZnO film can also be used in gas sensor [7] and other fields. Reading et al [8] deposited ZnO film on GaN-based LEDs, finding that white LEDs with ZnO sheet has higher luminous efficacy than devices with indium tin oxide film. Kim et al [9] successfully grew heteroepitaxial ZnO films in water at 90 C using a two-step method, and they also demonstrated that the aqueous solution can synthesis ZnO nanowire array film in the same growth system by changing its potential of hydrogen (PH).…”

The Influence of the Thermal Effect on CdSe/ZnS Quantum Dots in Light-Emitting Diodes

“…For the phosphor-free white LEDs, the laterally stacked structure of blue and green InGaN/GaN MQWs and monolithic polychromatic (LEDs) are demonstrated to grow white LEDs by multiple emission spectral and become the multicolor light-emitting sources [10], [11]. In addition, the ZnO current spreading is employed to compare the ITO due to lower sheet resistance and lower optical absorption [12].…”